Three pin frames are better, yes. You'll be fine with your two pin frame, though, as long as you stay with 9mm, and don't convert slide and barrel assemblies to, say, 40 caliber. There are different reasons, 'Why' 9mm and 40 caliber lock blocks peen the underside of Glock slides: In 9mm the original blocks were too poorly held in place; and in 40 caliber the original blocks were, both, too poorly held in place, AND the lock block, 'fingers' were too long. Here's some pictures of different Glock lock blocks for you to examine: